PC control and data processing in relation with a standalone laser beam analyzerT. Visan and D. G. Sporea Citation: Review of Scientific Instruments 71, 2610 (2000); doi: 10.1063/1.1150658 View online: http://dx.doi.org/10.1063/1.1150658 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/71/6?ver=pdfcov Published by the AIP Publishing

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REVIEW OF SCIENTIFIC INSTRUMENTS VOLUME 71, NUMBER 6 JUNE 2000

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PC control and data processing in relation with a standalone laser beamanalyzer

T. Visan and D. G. Sporeaa)

National Institute for Lasers, Plasma and Radiation Physics, Magurele, RO-76900, Romania

~Received 26 July 1999; accepted for publication 28 February 2000!

In this note we present a PC-based remote control and data processing setup and the associatedsoftware, developed in LabVIEW, working in conjunction with a laser beam analyzer. The setupexpands the imaging processing techniques for the laser beam profile, especially in relation to thethree-dimensional data representation and manipulation, by using the strong graphical processingand presentation libraries of theHIQ and IMAQ Vision software packages. One novelty of theproposed program consists in its multi-image processing ability with regard to images acquiredunder different conditions, and which have to be processed aligned to their centroids and their majoraxes. © 2000 American Institute of Physics.@S0034-6748~00!03706-0#

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In this note we address the problem that exists withmost all laser beam analyzers: data processing/presentatdone by the producer’s property software. In this way, itdifficult to integrate such instrumentation into more compsystems for data acquisition synchronization, databasesvelopment, and a unitary result presentation. In most staalone instruments, the communication software packagevided by the producer is also a very specific program, wno compatibility with some other software packages, whwould enable the product integration into a PC-controlcomplex setup.

The philosophy behind the software we developedbased on several simple and practical considerations.

~1! It should be used in conjunction with the SpiricoLBA-1001 laser beam analyzer, but it can be easadapted to any type of standalone instrument.

~2! The virtual instrument described in this note works wboth communication protocols, serial communicatiand a general purpose interface bus~GPIB! by using theindustrial standard data acquisition software LabVIEIn this way, through the virtual instrumentation concefull compatibility with other PC-controlled instrumentis assured, and complex experimental setups canbuilt, integrating, for example, data acquisition boarlaser characterization equipment, oscilloscopes, elecmechanical stages controllers, etc.

~3! Data processing/manipulation/visualization is done wthe software package associated with LabVIEW, namHiQ,2 but other popular software packages such as MLAB or Mathematica could be used. In this way, thalready existing strong data processing/manipulatsoftware libraries could easily be used.

~4! By using this programming approach, the programpropose is an open one. As compared to producproperty software that could not be modified/extend

a!Electronic mail: sporea@ifin.nipne.ro

2610034-6748/2000/71(6)/2610/2/$17.00

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by the user, our program enables the user to definefunctions/procedures3,4 for a specific application.

We started to build this virtual instrument by taking inaccount the fact that most standalone laser beam analyhave a communication port for data exchange and thatprogram has to be based on mathematical software availto many laboratories.

The virtual instrument we propose permits the serparallel transfer of the acquired image, embedding informtion on the modal distribution of the laser to be investigatand also performs a set of functions for remote control ofinstrument. For the case of communication through a GPwe used a National Instruments PCI-GPIB5 board. This pro-gram also calculates the basic parameters of the laser band meanwhile provides a fast three dimensional~3D!representation/manipulation6 of the laser intensity profile byaccessing IMAQ Vision graphical functions library. The avantage of using IMAQ Vision is that it is fully compatiblwith the National Instruments software. One of the functioperformed by the developed software is to remotely conthe laser beam analyzer unit. This communication canmade either by a serial RS 232 communication port or bymuch more efficient GPIB. The GPIB offers the advantathat more devices for laser beam investigation cancoupled to this bus and therefore many more parametersbe recorded with a temporal correlation between them. Tvirtual instrument controls communication with the lasbeam analyzer and one can set communication to any paeters corresponding to the communication port tyThrough these communications lines the user is able to scommands as strings of characters to the laser beamlyzer. These commands substitute for keyboard control oflaser beam analyzer unit and pass control to the remoteBy using these channels all parameters characterizinglaser beam already calculated by the laser beam analyzercan be read by the PC and used for further image procesand mathematical calculations. One of the most importparts of the program is the graphical interface becaus

0 © 2000 American Institute of Physics

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2611Rev. Sci. Instrum., Vol. 71, No. 6, June 2000 Notes

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ensures easy handling by the user. Therefore we transall functions of the keyboard of the laser beam analyzer othe computer screen and any command can be calledmouse click. In this way, an ergonomic interface is availato the user, an interface that mimics the corresponding cmands of the real instrument, similarly located for the useconvenience. New commands were also added, but areavailable in the remote control state. This is also improment of the device possibilities since one can very eaexplore a set of device functions that otherwise would hnot been possible.

For more complex processing of the acquired image,age data are passed as a matrix of 1203120 elements tocommon mathematical software. The matrix correspondan area of the charge coupled device~CCD! sensor, thereforethe dimensions in length units are proportional to the Csensor’s pixels dimensions/pitch. In our case the length ufor the x and y axes were equal to 0.033 mm. In this casHiQ 3.1 was used on the basis that LabVIEW alreadybuilt-in procedures for communication with HiQ. For othmathematical software packages the communication is mby object linking and embedding~OLE!. Once the image istransferred, a script is started in order to provide a thdimensional view of the laser beam profile and to calculits basic parameters, such as the major axis, the coordinof the centroid, etc. The mathematical script is designedprocess an image with emphasis on three dimensional resentation and to enable the user to modify or to add oprocessing algorithms. There are also some other imaprocessing procedures that are applied to the acquired im

These procedures are the following:

~1! fitting the surface corresponding to the image matwith a user defined functionf (x,y);

~2! mathematical operation involving two or more imagfor the evaluation of laser beam changes as it propagthrough different media and calculus of the laser bedivergence;

~3! image filtering designed for noise reduction;~4! cross sections made after planes described by equa

given by the user, zooming, rotating, etc.

In the case of evaluating the changes undergone blaser beam profile, the images acquired in different medialikely to be shifted from one to the other. This shift may leto significant errors in the image-processing proceduTherefore the proposed software first aligns the image fra

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to overlap their centroids and rotate the images to ovetheir major axes. In Fig. 1 is presented the differencetween the profile of a YAG–Nd laser beam and the profilethe same beam after phase conjugation in a multimode ocal fiber using stimulated Brillouin scattering. In this expement the initial pulse presents a Gaussian profile. In ordeevaluate the similarity between the conjugated pulse andpump pulse one has to subtract one from the other. The reof this subtraction is shown in Fig. 1 where it can be sethat the difference between profiles is not two Gaussianferences like expected, however the difference betweenimages is small compared with the their amplitude.

The virtual instrument presented can be interconnecto others programs and execute remote control on othervices~that can be power meters, spectrum analyzers, etc! inorder to control them at the same time. In this way a mcomplex investigation of the laser system can be perform

The authors want to thank to Spiricon, Inc. for donatithe LBA100 laser beam analyzer.

1Operator’s Manual, Spiricon Laser Beam Diagnostics, Laser Beam Alyzer, model LBA 100.

2HiQ User Manual, Bimillennium Corporation, 16795 Lark Avenue, Su200, Los Gatos, CA 95030.

3ISO / DIS 11145, Optics and Optical Instruments—Lasers and Laserlated Equipment—Vocabulary and Symbols~1995!.

4ISO / DIS 11145, Optics and Optical Instruments—Lasers and Laserlated Equipment—Test Method for Laser Beam Parameters: BeWidths, Divergence Angle and Beam Propagation Factor~1995!.

5NI-488.2M, Function Reference Manual for Win 32, National InstrumeCorporation, November 1995 Ed., Part No. 321038A-01.

6D. G. Sporea, G. Dumitru, and B. Prelipcean, Proc. SPIE3736, 328~1998!.

FIG. 1. 3D view of the difference between the conjugated pulse profilethe pump pulse profile.

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